Various performances required for automobile pneumatic tires include reduced rolling resistance, stability on a wet road and the like. As a method that can balance these properties, silica is compounded in a rubber composition for tires as a reinforcing filler. However, the following problem has been encountered: although silica is compounded in a rubber composition for tires, the dispersibility of silica into the rubber composition is low. Therefore, even in a case where a large amount of silica can be added, the effect of silica can not be fully obtained.
Patent Document 1 describes a method of manufacturing an elastomer/filler composite useful as a tire component and the like, the method comprising forming in situ a reinforcement filler from a precursor thereof in an elastomer•host material to uniformly disperse the reinforcement filler. In this case, in order to compound silica as a filler, a reaction from a filler precursor is required in Patent Document 1.
Patent Document 2 describes a method of manufacturing an elastomer/filler composite material, comprising: blending a filler precursor, a condensation reaction accelerator and an elastomer host (A) or (B) in a closed mixer to initiate a condensation reaction of the filler precursor; adding an organosilane material and a filler/filler precursor to the closed mixer before completion of the condensation reaction to allow for a reaction with regard to the elastomer host (A) and optionally the elastomer host (B); and collecting the resulting elastomer/filler composite material. Further the document states that this composite material may be used as an active ingredient of a rubber composition for tires, in particular a rubber composition for tire treads.
This document describes that the elastomer host (A) is a homopolymer of a conjugated diene or a copolymer of a conjugated diene and a vinyl aromatic monomer while the elastomer host (B) is an elastomer based on at least one diene terminally functionalized with alkoxy metal, wherein this diene based elastomer is represented by the following general formula (claim 5, paragraph [0014]):elastomer-X—(OR)n                 wherein elastomer: a homopolymer of a conjugated diene or a copolymer of a conjugated diene and a vinyl aromatic monomer                    X: a metal comprising Si, Ti, Al or B            R: a C1-C4 alkyl group            n: 3 for Si and Ti, and 2 for Al and B                        
However, Patent Document 2 only describes, in Examples, that styrene and 1,3-butadiene is copolymerized in an organic solvent in the presence of a lithium based catalyst, and then the resulting elastomer is collected. The document does not describe a method of manufacturing a terminal-modified polymer in which an —X—(OR)n group is introduced as an elastomer terminal group.
Further, Patent Document 3 describes a method of manufacturing a terminal acid anhydride group-containing polymer, comprising: allowing an ate complex comprising a living polymer and a typical metal element such as aluminum to react with a diester compound such as di-tert-alkyl maleate to prepare a polymer having a terminal diester group; and then the diester group is converted into an acid anhydride group.
With regard to the ate complex used in the above method, in a case where anionic polymerization of styrene is first performed using butyl lithium, a polymer terminal will become —C−Li+ unless the reaction stops. Li+ in this —C−Li+ belongs to a hard acid as used in the field of the HSAB theory, and therefore the paired —C− shows high reactivity. In general, the —C− being highly reactive (nucleophilic) also attacks a carbonyl carbon under this condition. As a result of this, introduction of an acid anhydride group is difficult. Therefore, it is carried out that a hard acid is often converted into a soft acid.
As a method of achieving this, an approach is used in the above patent document in which the reactivity is reduced by using a trialkyl aluminum compound having no leaving group, i.e., by transforming —C−Li+ into —C−(AlR3Li)+.